EASC 1000 - Topic 7: Plate Tectonics

Vocabulary flashcards covering the historical development of plate tectonic theory, evidence for continental drift, paleomagnetism, seafloor spreading, types of plate boundaries, the Wilson cycle, and Newfoundland Appalachian geology.

Sir Francis Bacon

The English philosopher who, as early as 1620, commented on the jigsaw fit of South America and Africa and speculated that the two continents might have once been connected.

Antonio Snider-Pellegrini

The French geographer who proposed a reconstruction of the globe with a closed Atlantic Ocean in his 1858 book 'La Création et Ses Mystères Dévoilés', attributing continental separation to Noah's flood.

Alfred Wegener

A German meteorologist (1880–1930) who formulated the modern scientific hypothesis of continental drift, publishing his evidence in 'The Origin of Continents and Oceans'.

Pangea

The late Paleozoic supercontinent proposed by Alfred Wegener that amalgamated all of Earth's landmasses into a single body, meaning 'all Earth'.

Glacial Striations

Linear scratches gouged into bedrock by moving glaciers that indicate the past direction of ice sheet flow across ancient continents.

Glossopteris

A Late Permian plant genus with approximately 200 known species whose fossilized tongue-shaped leaves are distributed across South America, Africa, Madagascar, India, Antarctica, and Australia.

Illawarra Coal Measures

A Late Permian sedimentary succession up to $150\,\text{m}$ thick in the Sydney Basin, Australia, composed of shale, sandstone, chert, coal, and torbanite seams bearing Glossopteris fossils.

Mesosaurus

A small, late Paleozoic coastal reptile unable to traverse open oceans whose fossils occur exclusively in matching rock strata of South America and southern Africa.

Bathymetry

The study and measurement of the depth, shape, and physical topography of the ocean floor surface.

Marie Tharp

A Columbia University scientist (1920–2006) who analyzed naval sonar data to produce the first detailed physiographic maps of the ocean floor, discovering the rift valley along the Mid-Atlantic Ridge.

Harry Hess

A geologist (1906–1969) who synthesized oceanographic bathymetry and sediment data in the early 1960s to propose the seafloor spreading hypothesis.

Seafloor Spreading

The tectonic process whereby new oceanic lithosphere forms from rising asthenospheric mantle along mid-ocean ridges and moves outward, widening ocean basins while older crust sinks at deep trenches.

Curie Point

The temperature threshold between $500$ and $700\,^{\circ}\text{C}$ above which magnetizable materials lose their permanent remanent magnetism.

Geothermal Gradient

The rate at which Earth's internal temperature increases with depth, averaging approximately $25\,^{\circ}\text{C/km}$, limiting permanent rock magnetization to depths above roughly $30\,\text{km}$.

Magnetic Epoch

A prolonged geological interval during which Earth's magnetic dipole is dominantly oriented in a single polarity state, either normal (north-pointing) or reversed (south-pointing).

Marine Magnetic Anomalies

Symmetric, alternating bands of normal- and reversed-polarity magnetism preserved in oceanic basalt parallel to mid-ocean ridges that document continuous seafloor spreading over time.

Lithospheric Plate

One of roughly 20 rigid segments (including 12 major plates) comprising Earth's lithosphere that glide across the underlying asthenosphere.

Active Margin

A continental boundary that directly coincides with a plate boundary, characterized by significant seismic activity, deformation, and frequently volcanism.

Passive Margin

A continental boundary that is not a plate boundary, characterized by thinned continental crust underlying an accumulation of younger sediments in a passive-margin basin.

Seismic Belts

Narrow geographical corridors exhibiting concentrated earthquake activity that delineate the boundaries between lithospheric plates.

Divergent Boundary

A boundary where two tectonic plates move apart from the axis of a mid-ocean ridge, accompanied by mantle melting and the creation of new oceanic lithosphere.

Oceanic Crust Stratigraphy

The characteristic layered sequence formed at divergent ridges, consisting from top to bottom of pillow basalts, vertical sheeted basaltic dikes, and slowly cooled gabbro.

Convergent Boundary

A plate boundary where two lithospheric plates advance toward each other, causing the denser oceanic plate to bend and descend into the mantle via subduction.

Deep-Ocean Trench

An elongate, steep-sided seafloor depression with depths up to $11\,\text{km}$ marking the zone where a downgoing oceanic plate flexes into the asthenosphere.

Volcanic Arc

A curving chain of active volcanoes generated above a subducting plate at depths around $150\,\text{km}$, where released fluids induce partial melting in the overlying mantle wedge.

Accretionary Prism

A wedge-shaped body of marine sediment and scraped trench fill that is structurally sliced and plastered onto the margin of the overriding plate during subduction.

Forearc Basin

A structural depression situated between the accretionary prism (or trench) and the front of the volcanic arc where eroded terrigenous sediment accumulates.

Back-Arc Basin

A marginal sea and extensional spreading centre developed behind a volcanic arc due to slab rollback or offshore subduction initiation.

Transform Boundary

A conservative plate boundary where plates shear horizontally past each other along vertical strike-slip faults without generating or consuming lithosphere.

San Andreas Fault

A major continental transform fault in California linking the Mendocino triple junction in the north to spreading segments in the Gulf of California in the south, sliding the Pacific Plate past the North American Plate.

Mantle Convection

A thermal engine driving plate motions through the buoyancy-driven overturn of asthenospheric mantle, where hot, less dense material upwells and cold, dense slabs sink.

Wilson Cycle

The recurring planetary cycle of continental rifting, ocean basin opening, subsequent subduction, ocean closure, and mountain-building continental collision.

J. Tuzo Wilson

A Canadian geophysicist (1908–1993) who proposed the cyclic opening and closing of ocean basins in his 1966 Nature paper and formulated the concept of transform faults.

Harold 'Hank' Williams

A Newfoundland geologist who produced the definitive tectonostratigraphic lithofacies synthesis of the Appalachian Orogen in 1978/1979, proving the existence and closure of the ancient Iapetus Ocean.

Iapetus Ocean

A proto-Atlantic Paleozoic ocean basin (~$500\,\text{Ma}$) named after the mythological father of Atlas that closed prior to Pangea's assembly, leaving suture belts preserved in the Northern Appalachians.

Humber Zone

The western tectonostratigraphic belt of Newfoundland, representing the ancient Grenvillian crystalline basement and Appalachian miogeoclinal passive margin of Laurentia.

Dunnage Zone

The central mobile belt subdivision in Newfoundland comprising obducted ophiolites, volcanic arc complexes, and deep marine sediments that represent the remnants of the Iapetus Ocean.

Gander Zone

The Appalachian tectonic zone in Newfoundland preserving deformed continental margin and shelf deposits of peri-Gondwanan affinity positioned east of the Dunnage suture.

Avalon Zone

The easternmost geological belt of Newfoundland comprising Late Neoproterozoic volcanic and sedimentary rocks derived from an exotic microcontinent of peri-Gondwanan origin.